Systems and methods for managing wireless communication links for hearing assistance devices

ABSTRACT

Various system embodiments comprise a plurality of devices adapted to wirelessly communicate with each other. The plurality of devices includes a battery-operated hearing assistance device adapted to be worn by a person. The hearing aid device includes a signal processing circuitry connected to a microphone and a receiver. At least one of the plurality of devices includes a link quality management device adapted to assess a link quality for a first wireless communication channel, provide channel metrics indicative of the assessed quality for the first wireless communication channel, and adjust wireless communication over the first wireless communication channel using the channel metrics for the first wireless communication channel.

CLAIM OF PRIORITY

The present application is a continuation of U.S. application Ser. No. 12/552,513, filed Sep. 2, 2009 which claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 61/094,021, filed Sep. 3, 2008, which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

This application relates generally to wireless networks and, more particularly, to systems, devices and methods for managing wireless communication links for hearing assistance devices.

BACKGROUND

Radio waves are electromagnetic waves that can be used in wireless communication. The frequencies of these waves serve as physical communication channels. The radio frequency (RF) spectrum has a finite range of frequencies, and thus a limited number of channels. In the United States, for example, the Federal Communications Commission (FCC) decides how the spectrum is allocated and what bands are used for what purpose.

Communication signals on the same channel interfere, assuming the strengths of the signals are non-negligible due to transmission power and distance. Also, communication signals on adjacent channels may interfere with communications on the desired channel because of inadequate filtering, tuning or frequency control. Adjacent channel interference can increase with an increase in signal power in adjacent channels.

Most countries of the world have allocated certain frequency spectrums for commercial use as “unlicensed” wireless bands. For example, the FCC has designated license-free bandwidth segments for industrial, scientific and medical (ISM) uses. Various commercial applications use this unlicensed bandwidth for short range wireless communication.

Channels are not allocated within the license-free band. Commercial devices designed to operate in the license-free band are constrained to transmit using a relatively low power, which allows more commercial devices to use the unlicensed frequency bands by increasing the reuse of a frequency. Spread spectrum systems mitigate interference by spreading their information over a much larger bandwidth than the information requires. This has the advantage of spreading any narrowband interference encountered within the channel over a large bandwidth which can then be integrated out by the receiver. The transmitter and receiver coordinate and manage the spreading sequences. This adds complexity and power to spread the signal using either fast frequency hopping or direct sequence phase manipulation. This added complexity and power may prevent these schemes from being used in ultra-low power communications systems.

SUMMARY

Various system embodiments comprise a plurality of devices adapted to wirelessly communicate with each other. The plurality of devices includes a battery-operated hearing assistance device adapted to be worn by a person. The hearing aid device includes a signal processing circuitry connected to a microphone and a receiver. At least one of the plurality of devices includes a link quality management device adapted to assess a link quality for a first wireless communication channel, provide channel metrics indicative of the assessed quality for the first wireless communication channel, and adjust wireless communication over the first wireless communication channel using the channel metrics for the first wireless communication channel.

Various system embodiments comprise a plurality of devices adapted to wirelessly communicate with each other. The plurality of devices includes at least one hearing assistance device. The hearing assistance device including a signal processing circuitry connected to a microphone and a receiver. The system includes means for assessing link quality for at least one wireless communication link between two devices, and means for adjusting wireless communication based on the assessed link quality.

According to various method embodiments, link quality is assessed for a wireless communication link between a battery-operated hearing assistance device and at least one other device. Wireless communication is adjusted based on the assessed link quality.

An embodiment of a hearing assistance device comprises an antenna, a first receiver connected to the antenna, and a second receiver connected to the antenna. The first receiver is configured to receive a signal through a data transmission channel at a first frequency. The second receiver is configured to scan available frequencies, provide at least one channel metric for each of the available frequencies, and determine an alternate frequency based on the at least one channel metric for each of the available frequencies. The first receiver is further adapted to provide at least one channel metric indicative of a quality of the first frequency, and change the data transmission channel to the alternate frequency when the at least one channel metric for the first frequency is indicative of poor data transmission quality.

This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate a wireless link between various embodiments of a hearing assistance device and a communicator.

FIG. 2A-2E illustrate a communicator operably connected to different devices, according to various embodiments.

FIGS. 3A-3E illustrate a communicator integrated within different devices, according to various embodiments.

FIG. 4 illustrates an embodiment of a wireless system with a wireless audio controller (WAC) and at least one hearing assistance device.

FIG. 5 illustrates various wireless communication environment(s) with a hearing aid device, according to various embodiments of the present subject matter.

FIG. 6 illustrates a wireless communication network within a multi-office environment with multiple programmers and hearing aids.

FIG. 7 illustrates a block diagram of a hearing aid embodiment.

FIG. 8 illustrates a block diagram of the communicator, such as a programmer.

FIG. 9 illustrates a wireless communication system embodiment.

FIGS. 10A-10B illustrate device embodiments with primary and secondary receivers.

FIGS. 11-13 illustrate embodiments of methods for managing wireless communication links.

FIG. 14 illustrates a state diagram of an embodiment of a process performed by a station to maintain link quality.

DETAILED DESCRIPTION

The following detailed description of the present subject matter refers to the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present subject matter. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope is defined only by the appended claims, along with the full scope of legal equivalents to which such claims are entitled.

FIGS. 1A-1D illustrate a wireless link between various embodiments of a hearing assistance device and a communicator. FIG. 1A illustrates a wireless communication link 100A between the hearing assistance device 101A and the communicator 102A. The communication link is used to communicate information. Examples of information include audio data or other data, commands, and programming instructions. In RF communication, the communication link uses a transmission frequency to establish the link in a communication channel. Examples of hearing assistance devices include both prescription devices and non-prescription devices. Examples of hearing assistance devices include hearing aids, headphones, assisted listening devices, earbuds, and the like. The communicator represents a device that communicates information to the hearing assistance device over the wireless communication link.

FIG. 1B illustrates the system of FIG. 1A, where the communicator includes a link quality management device. As will be described below, the link quality management device 103B assesses the quality of the communication link 100B, and controls the adjustments to the communication over the link. Some embodiments, the communication adjustments are made by the communicator 102B. Some embodiments send a command from the communicator 102B to the hearing assistance device 101B instructing the hearing assistance device to take an action in an effort to improve the quality of the wireless communication link. In some embodiments, when it is determined that an action should be taken to adjust communication and improve the link quality, the communicator makes an adjustment and sends a command to the hearing assistance device instructing the hearing assistance device to take an action to adjust communication and improve the link quality.

FIG. 1C illustrates the system of FIG. 1A, where the hearing assistance device includes a link quality management device. As will be described below, the link quality management device 104C assesses the quality of the communication link 100C, and controls the adjustments to the communication over the link. Some embodiments, the communication adjustments are made by the hearing assistance device 101C. Some embodiments send a command from the hearing assistance device 101C to the communicator 102C instructing the communicator to take an action in an effort to improve the quality of the wireless communication link. In some embodiments, when it is determined that an action should be taken to improve the link quality, the hearing assistance device makes an adjustment and sends a command to the communicator instructing the communicator to take an action to adjust communication and improve the link quality. In some embodiments, the hearing assistance device sends communications statistics such as CRC errors, SNR levels, FEC statistics, etc. to the host communications device so that it can take action to improve the link quality.

FIG. 1D illustrates the system of FIG. 1A, where both the hearing assistance device and the communicator include a link quality management device. As will be described below, the link quality management devices 103D and 104D assesses the quality of the communication link 100D, and controls the adjustments to the communication over the link. According to various embodiments, both link quality management devices monitor the link quality the same way, or the link quality management devices monitor different aspects of the link quality (e.g. distribute the link quality assessment). In some embodiments, only one of the devices operate its link quality management device to monitor link quality. The choice between the devices 103D and 104D can be made during communication initialization or can be preprogrammed. According to various embodiments, when it is determined that an action should be taken to improve the link quality, one or both of the devices 101D and 102D take an action to adjust communication and improve the link quality.

FIG. 2A-2E illustrate a communicator operably connected to different devices, according to various embodiments. The illustrated communicator 202 is a device adapted to be connected to another device as a peripheral device. For example, the device and the peripheral communicator can be connected via Wireless communication such as Bluetooth or WiFi or wired technology such as USB or firewire. The peripheral communicator can be connected to a variety of devices, such as to a programmer as illustrated in FIG. 2A, a hearing assistance device as illustrated in FIG. 2B, an assisted listening device as illustrated in FIG. 2C, a streaming audio device as illustrated in FIG. 2D, and a wireless audio controller (WAC) as illustrated in FIG. 2E.

FIGS. 3A-3E illustrate a communicator integrated within different devices, according to various embodiments. The illustrated communicator 302 is a device adapted to be integrated with or built within another device as a peripheral device. For example, the communicator can be an expansion card connected within a computer chassis. The communicator can be integrated with or built within a variety of devices, such as to a programmer as illustrated in FIG. 3A, a hearing assistance device as illustrated in FIG. 3B, an assisted listening device as illustrated in FIG. 3C, a streaming audio device as illustrated in FIG. 3D, and a wireless audio controller (WAC) as illustrated in FIG. 3E.

FIG. 4 illustrates an embodiment of a wireless system with a wireless audio controller (WAC) and at least one hearing assistance device. US 2006/0274747, entitled: COMMUNICATION SYSTEM FOR WIRELESS DEVICES, and U.S. Ser. No. 11/619,541, entitled: WIRELESS SYSTEM FOR HEARING COMMUNICATION DEVICE PROVIDING WIRELESS STEREO RECEPTION MODES, both of which are incorporated herein in their entirety, and include examples of WACs. The illustrated WAC 405 includes an I/O port 406 to a network 407 (e.g. Internet, LAN, WAN, WILAN, Bluetooth, Cellular, etc) through which data (e.g. compressed audio data) is communicated to the WAC. The illustrated WAC also includes at least one I/O port adapted for use to wirelessly communicate with at least one hearing assistance device. The illustrated WAC embodiment includes two I/O ports 408 and 409 adapted to be used to communicate with a hearing assistance device. For example, a first port can communicate a left channel and a second port can communicate a right channel to provide a wearer of the hearing aid devices with a stereo sound. If the link quality of one of the channels is determined to be undesirably low, the illustrated WAC is able to send the same signal to both hearing assistance devices. This signal can represent a monophonic signal to be presented to both of the hearing assistance devices, or can represent one channel of a stereophonic signal to be presented to both of the hearing assistance devices. The connection between the WAC 406 and the network 407 can be wireless, wired, or a hybrid of wired and wireless. Wireless communications can include standard or nonstandard communications. Some examples of standard wireless communications include link protocols including, but not limited to, Bluetooth™, IEEE 802.11 (wireless LANs), 802.15 (WPANs), 802.16 (WiMAX), 802.20 mobile wireless, cellular protocols including, but not limited to CDMA and GSM, ZigBee, and ultra-wideband (UWB) technologies. Such protocols support radio frequency communications and some support infrared communications. It is possible that other forms of wireless communications can be used such as ultrasonic, optical, and others. It is understood that the standards which can be used include past and present standards. It is also contemplated that future versions of these standards and new future standards may be employed without departing from the scope of the present subject matter. Wired communications include, but are not limited to, one or more mono or stereo connections or digital connections having link protocols including, but not limited to IEEE 802.3 (Ethernet), 802.4, 802.5, USB, ATM, Fibre-channel, Firewire or 1394, InfiniBand, or a native streaming interface. Such connections include all past and present link protocols. It is also contemplated that future versions of these protocols and new future standards may be employed without departing from the scope of the present subject matter.

FIG. 5 illustrates various wireless communication environment(s) with a hearing aid device, according to various embodiments of the present subject matter. The illustrated hearing aid device 510 is an in-the-ear hearing aid that is positioned completely in the ear canal 511. The present subject matter is not so limited, however. In addition to the illustrated in-the-ear style, the features of the present subject matter can be used in other styles of hearing assistance devices, including half-shell, in-the-canal, behind-the-ear, over-the-ear, eyeglass mount, implants, and body worn hearing aids, and further can be used in noise-protection earphones, headphones, and the like.

Referring again to FIG. 5, a wireless communication system in the hearing aid is adapted to communicate with one or more devices. In various embodiments, the hearing aid uses RF wireless communication to communicate with an external programmer 512. The programmer is able to adjust the hearing aid settings such as mode, volume and the like, to download a complete hearing aid program, and to receive data from the hearing aid for data logging, diagnostics, reporting and the like. In various embodiments, the hearing aid wirelessly communicates with an assisted listening system 513 to receive an audio signal, or a device 514 that provides encoded and compressed audio, or a remote control device 515, or another hearing aid 516, or various combinations thereof.

One challenging environment for hearing aid wireless communication involves a multi-office environment where several programmers may be within range of one another and attempt to discover nodes (e.g. hearing aids) simultaneously. In addition many nodes may be within range of each programmer. Furthermore, the multi-office environment may include other wireless services and/or otherwise devices that emit electromagnetic radiation that may adversely affect the desired wireless communication.

FIG. 6 illustrates a wireless communication network within a multi-office environment with multiple programmers and hearing aids. Any of the programmers 612 are capable of discovering and communicating with hearing aids 610. Further, the programmers 612 can be wirelessly networked together, such as illustrated by the wireless network 617. Additionally, some hearing aids (e.g. left/right hearing aids for a patient) can be designed to wireless communicate with each other in addition to the programmers 612 or other communicators.

Some hearing aid embodiments incorporate a scanning feature to reduce the probability of interference. The probability that interference is on multiple channels simultaneously is significantly less, since the conditional probabilities for independent events are multiplied together for the overall probability that both channels will simultaneously experience interference. Interference can increase the duty cycle of the receiver since the detection of energy on a channel above a Receive Signal Strength Indicator (RSSI) threshold causes the receiver to stay awake. Thus, interference can adversely impact the battery life of the hearing aid. Some embodiments use a wake timer that, if the receiver is awake longer than the sleep cycle without receiving a valid packet, causes the receiver to go into a deep sleep mode with a longer sleep cycle until the interference goes away.

A system, such as the one illustrated in FIG. 6, performs a process to discover the nodes in operational proximity. Any number of channels can be assigned as discovery channels. The use of two or more discovery channels considerably increases the odds of successful links in comparison to a single discovery channel as the single channel may already be in use. These channels are reserved for node discovery of hearing aids by programmers. Programmers pick a desirable discovery channel based on a link quality assessment (LQA). Hearing aids scan the discovery channel frequencies prior to establishing a programming link. During discovery, programmers ping for nodes using a broadcast discovery message that is sent out at random intervals. The node is registered with the programmer if an acknowledgement is received by the programmer. Hearing aids register with all programmers in discovery mode within range of the hearing aid, and associate with programmers after being discovered and selected via the programmer's user interface. Once nodes are discovered, the user is notified using the user display of the hearing aids that are within range. The user then can select the nodes with which to establish a link.

Various programmer embodiments use a LQA table which is updated by scanning each available channel and is used by the programmer to determine a desirable channel, on which to establish a wireless communication session, among the available channels. The programmer sends a frequency change message to each hearing instrument. This message is acknowledged by the hearing aid. Normal data transfer to and from the hearing instrument can begin once the link has been established on the desired channel. Some programmer embodiments perform intermittent (e.g. periodic) maintenance throughout the wireless communication session. In some embodiments, the host communications device sends a maintenance message that contains the next available channel in case the link is lost due to interference as well as a transmit power control word. The channel maintenance response from the hearing instrument contains several communications metrics such as the number of successful packets received since the last maintenance response and the number of packets containing errors. This information is used by the programmer to determine the downlink quality and the uplink quality. The programmer is able to determine the downlink quality by comparing the number of no acknowledgments with the number of messages received by the hearing instrument. In addition to statistics collected during maintenance, some programmer embodiments monitor the RSSI of the nodes on each packet received. Some embodiments maintain this signal strength as a moving average in time. The signal strength can be used to adjust the power control of the uplink signal from the nodes. Adjustments can be made during maintenance messages. The links can operate on the fringe of link margin. However, if there is sufficient link margin, various embodiments allow for upstream power reduction (transmission from remote nodes/hearing aids to the host communications device) to save power in the remote nodes. As is discussed below, there are a number of ways to assess the link quality of RF communication links and a number of ways to adjust the RF communication based on the assessed link quality.

FIG. 7 illustrates a block diagram of a hearing aid embodiment. The illustrated hearing aid 710 includes a microphone system 718, a signal processing circuit 719 which may be incorporated as part of a controller, and a speaker 720 referred to as a hearing aid receiver. The microphone system 718 transforms the acoustic energy 721 of sound from an acoustic source 722 into a signal representative of the sound. The signal processing circuit 719 receives the signal from the microphone system 718, and is designed (e.g. programmed) to appropriately adjust the signal to compensate for the hearing impairment of the wearer of the hearing aid. The signal processing circuit 719 outputs a processed signal to the hearing aid receiver 720, which converts the processed electrical signal into a sound perceived by the wearer. The illustrated hearing aid embodiment also includes a wireless communication circuit 723 adapted to transmit and/or receive wireless signals. The wireless communication circuit may include a receiver, a transmitter, or a transceiver. The signal processing circuit 719 (or controller) controls the wireless communication circuit 723 to control the wireless communication with other devices.

FIG. 8 illustrates a block diagram of the host wireless communicator, such as a programmer. The illustrated communicator includes a controller 824 and a wireless communication circuit 825 adapted to transmit and/or receive wireless signals. The wireless communication circuit may include a receiver, a transmitter, or a transceiver. The controller 824 controls the wireless communication circuit 825 to control the wireless communication with other devices. The station can include other elements, such as various input/output devices like a display monitor, keyboard and mouse.

FIG. 9 illustrates a wireless communication system embodiment. The illustrated system includes a number of devices adapted to wirelessly communicate with at least one other device in the system. The devices in the system illustrated in FIG. 9 include a host communicator such as illustrated in FIG. 8, and further include first 910R and second 910L hearing aids, such as illustrated in FIG. 7 and as may be simultaneously worn to assist hearing in a person's right and left ears. As illustrated by the dotted lines in FIG. 9, the communicator is adapted to wireless communicate with both hearing aids, the first hearing aid is adapted to wirelessly communicate with the second hearing aid and the communicator, and the second hearing aid is adapted to wirelessly communicate with the first hearing aid and the communicator. The communication signals may include data and/or audio. Examples of data include programming instructions, device diagnostics, and link quality information. Examples of audio include digital audio or compressed digital audio.

FIGS. 10A-10B illustrate device embodiments with primary and secondary receivers. FIG. 10A illustrates a device embodiment with an antenna 1026, and a primary receiver 1027 and a secondary receiver 1028 connected to the antenna. The antenna can include spacially-diverse antennas, an antenna with diverse polarities, or spacially-diverse antennas with diverse polarities. The primary receiver 1027 receives a data communication using the antenna, and the secondary receiver 1028 scans other possible communication channels to assess the link quality of these other channels in anticipating of switching the channel used by the primary receiver. In the illustrated embodiment, the secondary receiver 1028 provides a list of next best channels, and provides the primary receiver with the next best alternate channel. The primary receiver 1027 receives the data communication through a channel, monitors channel metrics indicative of channel quality for the channel used to receive the data. Examples of channel metrics include bit error rate (BER), packet error rate (PER), cyclic redundancy check (CRC) errors, forward error correction (FEC) errors, signal to noise ratio (SNR), and the number of retransmissions.

FIG. 10B provides a more detailed illustration of a device embodiment with an antenna 1026, and primary and secondary receivers. The illustrated antenna 1026 is a spacially diverse antenna and/or has diverse polarities. A received signal passes through a low noise amplifier (LNA) 1029, and then passes to both a primary and a secondary receiver.

The primary receiver includes a local oscillator (LO) 1030 which is programmed to oscillate at a frequency necessary for communications. A mixer 1031 multiplies the signal from the LNA with the signal from the LO 1030, and outputs the resulting modulated signal to a bandpass filter 1032. A demodulator 1033 demodulates the modulated signal to provide the data from the signal to a gate 1034 and to a correlator 1035. The modulated signal is also presented to a Receive Signal Strength Indicator (RSSI) module 1036 that compares the strength of the received signal to a threshold and outputs the signal level to the correlator 1035. The correlator controls the timing of the received signal level and the received data to allow the data to pass through the gate when the signal level is above the RSSI threshold and when a correlation word is received. A multiplexer 1037 outputs a data signal level when data is received (Y=1) and outputs a noise signal level when data is not received (Y=0), which are used to determine a signal to noise ratio (SNR). The SNR can be used to change the diverse antenna. For example, an antenna currently being used can be exchanged for a spacially-diverse antenna and/or a polarity of an antenna can be changed. The SNR measurement can be used to switch to an alternate channel. If the SNR is less than a threshold, the next best alternate channel is used for the data transmission. The data passed through the gate can be presented to an error rate detector 1038 which can determine the error rate on a bit or packet basis, and can be presented to a module 1039 to extract channel maintenance messages embedded in the data. Examples of channel maintenance messages include the number of good received packets, the number of CRC errors, the number of FEC errors, and the number of retransmissions sent by a node. This information can also be used to determine when to change the diverse antenna and/or change channels.

The secondary receiver includes a scanning local oscillator (LO) 1040 that scans frequencies corresponding to available channels. A mixer 1041 multiplies the signal from the LNA with the signal from the scanning LO 1040, and outputs the resulting modulated signal to a bandpass filter 1042. A Receive Signal Strength Indicator (RSSI) module 1043 measures the strength of the received signal and outputs the signal level to quality measurement module 1044 adapted to monitor the quality of potential communication channels based on noise levels. An LQA ranking module 1045 ranks the available channels based on their link quality e.g. channels with lower noise rank higher than channels with higher noise. A table 1046 is used to store entries with frequencies of available channels, along with a quality rank for each entry. The table can be used to provide the highest ranking channel as the next available channel to replace the current working communication frequency in the primary receiver. The channel quality metric is formed using both a peak detector and an RMS detector.

FIG. 11 illustrates a method for managing wireless communication links according to various embodiments of the present subject matter. The link quality of a wireless communication link is assessed at 1147, and the wireless communication is adjusted at 1148 based on the assessed link quality.

FIG. 12 illustrates a method for managing wireless communication links according to various embodiments of the present subject matter. A first link quality metric is determined at 1249; and at 1250, communication is adjusted based on the first link quality metric. A second link quality metric is determined at 1251; and at 1252, communication is adjusted based on the second link quality metric. Some embodiments continue this determination and adjustment to an nth time, such that an nth link quality metric is determined at 1253; and at 1254, communication is adjusted based on the nth link quality metric. The determination of a link quality metric (e.g. 1249, 1251, or 1253) can be based on an assessment of one or more aspects of the communication link, and the assessment(s) of the aspect(s) of the communication link can be performed simultaneously or according to various sequences. By way of example, and not limitation, an embodiment determines a first link quality metric by assessing the signal strength on the channel, a second link quality metric by assessing a signal to noise ratio, and a third link quality metric by assessing the combination of signal to noise ratio, error rate, and a number of retransmissions being required for sending a packet.

FIG. 13 illustrates a method for managing wireless communication links according to various embodiments of the present subject matter. The link quality of a wireless communication link is assessed at 1347, and the wireless communication is adjusted at 1348 based on the assessed link quality. According to various embodiments, the link quality of a wireless communication link is assessed using a signal to noise ratio for a link 1355, a bit error rate for the link 1356, a number of retransmissions for a link over a period of time 1357, or various combinations thereof. The figure illustrates some examples of ways to assess the current communication channel's link quality. Any one or any combination of assessments may be performed simultaneously or in various sequences to provide a link quality assessment. LQA is discussed in further detail below. According to various embodiments, adjusting wireless communication includes adjusting transmission power 1358, adjusting a symbol rate of transmission 1359, adjusting a Receive Signal Strength Indicator (RSSI) threshold 1360, adjusting a packet length 1361, adjusting selection of a diverse antenna 1362 (e.g. spacially-diverse and/or diverse in polarity), adjusting a transmission frequency (channel hopping) 1363, and adjusting receiver gain based on RF environment detected across all or a subset of available channels 1364. It is understood that in various embodiments, adjustments may be done outside of during channel maintenance times. For example, in various embodiments a channel change may be performed when a packet is not acknowledged for a number of retries, which may be performed outside of a maintenance interval. Other adjustments are possible and those provided herein are not intended to be exhaustive or limiting.

Link Quality Assessment (LQA)

Battery-powered remote devices that function as hearing assistance devices (e.g. hearing aids) transmit with limited power, such that, as seen by the receiver of the transmission (e.g. communicator or other hearing aids), the transmission is near the noise floor of the occupied channel. Communication with low power devices, having little power available for transmit, will have minimal link margin. A high data throughput can be achieved using a low power RF link when the link is of good quality. However, multi-path fading, interference, body and head shadowing, and increased range potentially impair the link.

An assessment of link quality for a wireless communication channel can be made by assessing noise in the channel, or signal strength in the channel, or a signal to noise ratio for the channel, or a bit error rate, or a packet error rate, or the number of retransmissions, or various combinations thereof.

Wireless Communication Adjustments Based on LQA

The present subject matter uses LQA information, also referred to herein as channel metrics, for wireless communication channels to manage and make adjustments to the wireless communication.

Power

Various embodiments of a wireless communication system with hearing aid nodes use variable power levels for the transceiver based on channel quality metrics. Some embodiments use link quality metrics to control transmit RF power of devices using the link for communicating to, from or between hearing aids. Some embodiments use link quality metrics to control receiver input power consumption (e.g. receiver gain vs. linearity) for devices communicating to, from, or between hearing aids. Some embodiments automatically control gain of the receiver based on the RF environment (see, for example, US 2007/0110193 entitled Automatic Gain Control With Out Of Band Blocking Signal Compensation, which is incorporated by reference in its entirety).

A decision metric is used to change power levels used on a wireless communications channel. Various embodiments employ adaptive transmit and receive power levels based on several channel metrics to improve power consumption and the link margin of the overall system. At any time during the communication session, the system may change transmit power levels or reduce the receiver power based on channel metrics used to assess link quality.

If the link from a station to a hearing aid (downstream link) is good, the station can lower its output power based on downstream link quality metrics in order to reduce its power consumption and potential interference with other such devices within range. The hearing aid may decide to lower its receiver gain and or linearity to conserve power when the downlink from the station is above an acceptable level of performance. If the link from the hearing aid to the station is good, the station may command the hearing aid to lower its transmission output power to improve the overall battery life of the hearing aid. If the link is poor, power may be increased to the extent permitted by power constraints for the device and system design to improve link margin.

If it is determined that the channel has a poor link quality, various embodiments increase RF power to maintain the link while maintaining the overall information throughput, various embodiments reduce the gain and linearity of the hearing aid's receiver to reduce the overall power consumption of the hearing aid when the link is of sufficient quality to warrant a reduction in receive performance.

Symbol Transmission Rates

Various embodiments of a wireless communication system with hearing aid nodes use various symbol rates based on channel quality metrics. A decision metric is used to change symbol rates a wireless communications channel employed for use with a hearing communication device. Various embodiments employ lower/higher symbol rates based on one or more channel metrics to improve the link margin of the overall system. At any time during a communication session, the system may change symbol rates based on channel metrics used to assess link quality.

Several methods for changing the symbol rate may be employed. For example, some embodiments employ a binary set of frequency shift key (FSK) symbols that alternate at the symbol rate. These symbols which control the symbol rate can be contained in the preamble, the sync word, or the message body. The receiver can then adapt its data recovery and pre and post detection filtering based on the symbol rate of the preamble, the sync word or the message body. If it is determined that the channel has a poor link quality, various embodiments reduce the symbol rate to maintain the link while lowering the overall throughput. If the channel's link quality is good or has improved, the symbol rate will increase to the extent permitted for the link quality.

Receive Signal Strength Indicator (RSSI) Threshold

A packet receive state machine in a receiver uses a RSSI threshold to determine the start of a packet transmission. Various embodiments of a wireless communication system with hearing aid nodes use an adaptive RSSI threshold. A decision metric is used to change the RSSI threshold on the packet receive state machine used on a wireless communications channel employed for use with a hearing communication device. The receiver state machine employs an RSSI threshold detector, a carrier recovery circuit, a timing recovery circuit, and a sync word correlator to determine the start of a packet reception.

Because the power-limited hearing aid transmits near the noise floor, the receiver (e.g. station) sets the RSSI threshold very close to the noise floor of the receiver but sufficiently high to avoid false detection on noise. If the receiver falsely identifies noise as a communication signal, the noise starts the receiver state machine which may make incorrect decisions on carrier and timing recovery (false detects) which will then prevent the actual packet from being optimally decoded by the receiver. These false detects can be avoided by setting the RSSI threshold appropriately above the noise floor of the receiver.

Since the system uses an unlicensed band, various sources of interference may appear from time to time on the channel of interest. These interferers cause the noise floor of the channel to vary with time. To account for this, various embodiments use an adaptive RSSI threshold to increase link margin (if available) in receiving a packet from a low powered remote hearing instrument. Various embodiments adjust this threshold more or less continuously and set the threshold during periods of non-packet activity on the channel, usually prior to or just after a packet is received. Some embodiments measure RSSI on a per packet basis and set the threshold as high as practical based on the quality of the link using RSSI values attained during and between packet reception.

If at any time during the session, the system may change the RSSI threshold based on based on channel metrics used to assess link quality. In addition to determining if the error rate falls below an acceptable level or the number of transmissions rises above an acceptable level, the RSSI can be deemed unacceptable for reliable communication based on the level of signal strength as measured in between packet receptions (quiet times), based on the level of signal strength as measured during packet reception, or where the signal to noise ratio has improved or been reduced, a combination of signal strength as measured in between packet receptions (quiet times) and as measured during packet reception.

For example, a station or programmer embodiment performs a channel maintenance algorithm, and adjusts the RSSI threshold for receiving a packet based on the number of retransmissions attempts and the number of checksum errors counted since the last channel maintenance window. If the number of errors and retry attempts indicate a packet error rate higher than 12%, for example, the programmer monitors the channel's noise floor to adjust the RSSI threshold.

Packet Length

Various embodiments of a wireless communication system with hearing aid nodes use various packet lengths based on channel quality metrics. A decision metric is used to change packet lengths a wireless communications channel employs for use with a hearing communication device. Various embodiments employ shorter/longer packet lengths based on one or more channel metrics to improve the link margin of the overall system. At any time during a communication session, the system may change packet lengths based on channel metrics used to assess link quality. If it is determined that the channel has a poor link quality, various embodiments shorten the packet length. If the channel's link quality is good or has improved, various embodiments lengthen the packet length to the extent permitted for the link quality.

Diverse (Spacial/Polarity) Antenna

Various embodiments of a wireless communication system with hearing aid nodes use diverse antenna(s), and change the diverse antenna(s) based on channel quality metrics. For spacially-diverse antennas, the current antenna can be switched with another antenna. For an antenna with diverse polarities, the polarity of the antenna can be switched. A decision metric is used to change/combine antennas used on a wireless communications channel employed for use with a hearing communication device.

In an indoor environment there are many sources of radio frequency reflections that cause multi-path signal arrivals at the antenna that may cause fading of the channel which effect the bit error rate or packet error rate of the system. Multi-path effects serve to enhance or destroy the signal link between the programmer and the hearing instrument. A diversity antenna system employing both polarization and spacial diversity can help to enhance the link. Even body shadows that may affect the main line of sight path may be mitigated by a random multi-path reflection from the ceiling or nearby wall. By employing a diversity antenna, the system improves the chances of intercepting a signal from the ceiling, floor, or nearby wall that is not impaired by body shadowing effects or even other interference.

Some embodiments choose on a per packet basis the best antenna to employ based on the best signal level or signal to noise ratio as measured during the preamble of the signal. Some embodiments demodulate the signal from two or more receiver/antenna pairs and keep the packet with the least errors or no errors. Some embodiments choose one of two or more antennas based on channel metrics such as receive signal strength, packet checksum errors, packet forward error correction errors, packet retransmission attempts. If at any time during the communication session, the system changes antennas based on channel metrics used to assess link quality.

For example, various station/programmer embodiments perform a channel maintenance algorithm. After the programmer tries to adapt the RSSI threshold, the programmer switches, based on the assessed link quality, to the opposite polarity antenna to determine if a null due to multi-path or undesirable antenna orientation can be mitigated using another antenna polarization or a spacially-diverse antenna. The switch can be based on the number of retransmissions attempts and the number of checksum errors counted since the last channel maintenance window. Should the number of errors and retry attempts indicate a packet error rate higher than 10%, for example, over the channel maintenance window, the programmer switches the antenna just prior to station maintenance. Some embodiments do not switch the antennas unless both nodes have acknowledged recent station maintenance messages containing the same alternate channel information. This way if the link is lost following diversity antenna switching, the nodes will rendezvous on the alternate channel together.

Transmission Frequency (Frequency Hopping)

Various embodiments of a wireless communication system with hearing aid nodes adjust transmission frequencies, or channel hop, based on channel metrics. Some system embodiments use a secondary “look ahead” receiver to select a desirable channel that is not corrupted by interference. Some system embodiments select a good channel using a primary receiver that time multiplexes its task of communication with a remote device and looking ahead for a good channel within the bandwidth. Some system embodiments use a Fast Fourier Transform (FFT) analysis to simultaneously evaluate all potential narrow band channels for potential use by a primary narrow band transceiver. Some system embodiments use a FFT analysis to look ahead at all potential channels while simultaneously communicating with a narrow band remote transceiver.

At any time during the communication session, the system may change channels based on channel metrics used to assess link quality for the current channel and for available channels. Because of the low power nature of the remote transceivers and the availability of a limited bandwidth resource, some embodiments use narrow band channels with time division multiple access and a listen before talk algorithm that allow frequency reuse with various other services.

A secondary receiver monitors the usage of an unlicensed band to pick a desirable channel for communicating information to and/or from a power-limited device. A primary transceiver communicates with a remote device using narrow band channels using a modulation scheme sufficient to convey information to and/or from a remote device. The primary receiver picks a desirable channel to use based on a channel metric found and stored by the secondary receiver that is continuously scanning the entire available bandwidth looking for adequate channels for communication to the remote devices. The secondary receiver uses a bandwidth that is substantially the same as the primary receiver so that a good assessment can be made of how that channel would perform when used for communication by the primary receiver.

If the channel is corrupt then the primary receiver within the base station will not be able to receive the remote signal and information cannot be conveyed in the up link. The down link transmission from the station to the hearing aid does not have the same power restrictions since the base unit has more power available and is restricted only by the regulations governing the output power within the unlicensed band. Armed with this knowledge the base station unit can make certain assumptions about the downlink. For instance based on the link quality assessment (LQA) made by the primary receiver or the secondary receiver it may or may not assume that the remote device can hear its signal. In most cases the downlink is robust enough to assume that a command can be received by the remote device even if the remote device cannot acknowledge its receipt. In this way the base station primary transmitter can command the remote device to move or “hop” to a different channel within the unlicensed band determined by the LQA made of all other possible channels within the unlicensed band by the secondary receiver. Once the command is made to send the remote to another viable channel the confirmation of the frequency change command can be made with the remote device on the new channel.

Various embodiments use a metric that involves both a peak and average detector. Channels that exhibit low peaks as well as low average values will show up as a high score and are a desirable channel for wireless communication. Channels having high peaks but low averages may work well for a listen-before-talk time division multiple access system, and thus receive a medium score. The system prefers to use a channel with a high score, but can use a channel with a medium score. Channels occupied by continuous narrow band signals will have a high average receive signal strength and would show up as a poor score. Several metrics can be formed using an assigned weight. Examples of metrics include: M_(chan)=; W₁*RSSI_(avg)+W₂(RSSI_(peak)); and M_(chan)=(RSSI_(avg)+RSSI_(peak)) RSSI_(avg). A higher weight is assigned to the average received signal strength than to the peak since Time Division Multiplex (TDM) and Listen Before Talk (LBT) systems may be able to be used.

For example, various station/programmer embodiments perform a channel maintenance algorithm. After the programmer tries to adapt the RSSI threshold and switch the antenna polarization, the programmer commands the hearing aid to channel hop to the next best channel taken from the LQA data of available channels. This channel hop is based on the assessed link quality (e.g. the number of retransmissions attempts and the number of checksum errors counted since the last channel maintenance window). Should the number of errors and retry attempts indicate a packet error rate higher than 22%, for example, over the channel maintenance window, the programmer can either command the hearing instrument to change channels using a channel change message or alternatively stop sending channel maintenance messages which will force the node to change channels.

If a single node is lost (no longer responding to channel maintenance messages), it can be assumed to have changed channels to the alternative channel that was last acknowledged by the node during a previous channel maintenance message. Because the nodes are vulnerable to falling out of range or being interfered with, various embodiments maintain the same alternate channel unless the alternate channel, based on current LQA information, is severely degraded from its initial quality assessment.

Receiver Gain in Hostile RF Environment

Some device embodiments are equipped with a secondary receiver that can be employed to access the quality of the available channels. According to some embodiments, this secondary receiver is also equipped to access the overall RF power in the band of operation. If the overall power across the band is above a certain threshold then the environment can be considered “hostile” for communications between devices. Some embodiments reduce the front end gain of the receiver to prevent overload. The reduced front end gain allows the communications link to be maintained at a reduced range of operation. For example, a reduced front end gain in some embodiments still allow communication over a distance on the order of 1.5 meters. Without this change in front end receiver gain a hostile RF environment allows the receiver to become over-loaded by the hostile RF environment.

Various embodiments reduce one or more of the AGC_Gain, AGC_Max Gain or the AGC_Search_Gain parameters of the receiver. Some embodiments determine a LQA score for each available channel that is not currently being used for communication, and then sums the LQA scores for all of these channels that are not currently being used. The United States, for example, in one embodiment has 28 available channels. If one of the channels is being used for communication, the LQA score of the remaining 27 channels is summed and compared to a threshold. In another embodiment, four channels are available in the European Union. If one of the channels is being used in the European Union, the LQA score of the remaining 3 channels is summed and compared to a threshold. If the sum of the LQA scores exceeds a threshold for lowering gain, then the receiver gain is lowered. Some embodiment lower the gain by one incremental value (e.g. on the order of 4 dB from nominal gain). The nominal gain for a band, such as within the United States, is determined during device calibration and is stored along with other band information in non-volatile memory. In one embodiment the threshold score will be given by T*(N−1) where N is the number of channels being scanned minus one (the channel in use). Where T will be the based on a factory calibration or a general metric of the compression point of the receiver.

FIG. 14 illustrates a state diagram of an embodiment of a process performed by a communicator to maintain link quality according to one embodiment of the present subject matter. The normal operation occurs at state 1465. During normal operation, the average noise, signal-to-noise ratio (SNR), and packet error rate (PER) are computed periodically. The period of time in which certain variables are computed is known as a “channel maintenance interval”. At the conclusion of a channel maintenance interval, some of the parameters are evaluated against corresponding thresholds such as PER and BER. If the PER is greater than the PER threshold, the station changes channels as illustrated at state 1468. In some embodiments, if the PER is greater than the PER threshold, the station adjusts a diversity antenna switch as illustrated at state 1467. In some embodiments, the station may first adjust the diversity antenna switch, re-evaluate the PER and then change channels if the PER is still greater than the PER threshold. If the SNR is less than the SNR threshold, the station adjusts a diversity antenna switch as illustrated at state 1467. In the embodiment of FIG. 14, if the average noise is not equal to the RSSI threshold plus a margin, the control adapts the RSSI threshold as illustrated at state 1466. IN some embodiments, if the packet retry count exceeds a packet retry count threshold, the station changes channels as illustrated at state 1468.

Other embodiments assess the link quality using a different order. Still other embodiments use different techniques to assess link quality, such as based on signal strength, environmental noise strength, signal to noise ratio, and retransmission counts. Various combinations of the different means for assessing link quality can be used. The different methods for assessing link quality can be performed in a number of different orders. The state diagram illustrated in FIG. 14 is provided as an example. Additionally, the process illustrated in the state diagram of FIG. 14 can be implemented in a variety of devices, including communicators and hearing assistance devices.

One of ordinary skill in the art will understand that, the modules and other circuitry shown and described herein can be implemented using software, hardware, and combinations of software and hardware. As such, the terms module and circuitry, for example, are intended to encompass software implementations, hardware implementations, and software and hardware implementations.

The methods illustrated in this disclosure are not intended to be exclusive of other methods within the scope of the present subject matter. Those of ordinary skill in the art will understand, upon reading and comprehending this disclosure, other methods within the scope of the present subject matter. The above-identified embodiments, and portions of the illustrated embodiments, are not necessarily mutually exclusive. These embodiments, or portions thereof, can be combined. In various embodiments, the methods are implemented using a data signal embodied in a carrier wave or propagated signal, that represents a sequence of instructions which, when executed by one or more processors cause the processor(s) to perform the respective method. In various embodiments, the methods are implemented as a set of instructions contained on a computer-accessible medium capable of directing a processor to perform the respective method. In various embodiments, the medium is a magnetic medium, an electronic medium, or an optical medium.

The above detailed description is intended to be illustrative, and not restrictive. Other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 

1. (canceled)
 2. A system, comprising: a first hearing assistance device configured to be worn by a person; a second hearing assistance device configured to be worn by the person; each of the first and second hearing assistance devices including a microphone, a receiver, and signal processing circuitry connected to the microphone and the receiver, wherein each of the first and second hearing assistance devise is battery-operated and is configured with wireless communication capabilities and is configured to use the wireless communication capabilities to wirelessly transmit audio data; a link quality management device configured to: assess link quality for a first wireless channel over which the first hearing assistance device transmits audio data and a second wireless channel over which the second hearing assistance device transmits audio data, and control, using the assessed link quality, wireless communication with the first and second hearing assistance devices.
 3. The system of claim 2, wherein: the first hearing assistance device is configured to generate the digital audio signal transmitted over the first wireless channel from a signal from the microphone in the first hearing assistance device; and the second hearing assistance device is configured to generate the digital audio signal transmitted over the second wireless channel from a signal from the microphone in the second hearing assistance device.
 4. The system of claim 3, wherein the link quality management device is configured to demodulate each the audio data signals transmitted over the first and second wireless channels, and keep packets with the least errors.
 5. The system of claim 2, wherein the link quality management device is configured to determine the wireless channel with the least assessed link quality, and avoid use of the wireless channel determined to have the least assessed link quality.
 6. The system of claim 2, wherein to assess the link quality the link quality management device is configured to: assess an error rate for the first wireless channel, where the channel metrics includes channel metrics indicative of the assessed error rate; or count retransmissions for the first wireless channel, where the channel metrics include channel metrics indicative of the retransmissions.
 7. The system of claim 2, wherein the link quality management device is configured to: adjust power to transmit or receive a signal over the first wireless communication channel using the channel metrics for the first wireless communication channel; adjust a symbol transmission rate over the first wireless communication channel using the channel metrics for the first wireless communication channel; adjust a packet length of a signal over the first wireless communication channel using the channel metrics for the first wireless communication channel; adjust selection or combination of a diverse antenna using the channel metrics for the first wireless communication channel; or change frequencies using the channel metrics for the first wireless communication channel.
 8. A method, comprising: receiving an audio data signal wirelessly transmitted over a first wireless channel from a first hearing assistance device configured to be worn by a person; receiving the audio data signal wirelessly transmitted over a second wireless channel from a second hearing assistance device configured to be worn by the person, each of the first and second hearing assistance devices including a microphone, a receiver, and signal processing circuitry connected to the microphone and the receiver, wherein each of the first and second hearing assistance devise is battery-operated; assessing a link quality for a first wireless channel over which the first hearing assistance device transmits the audio data signal and a second wireless channel over which the second hearing assistance device transmits the audio data signal; providing channel metrics indicative of the assessed quality for the wireless channels; and controlling, using the channel metrics, wireless communication with the first and second hearing assistance devices.
 9. The method of claim 8, further comprising: generating the digital audio signal transmitted over the first wireless channel from a signal from the microphone in the first hearing assistance device; and generating the digital audio signal transmitted over the second wireless channel from a signal from the microphone in the second hearing assistance device;
 10. The method of claim 9, further comprising demodulating each the audio data signals transmitted over the first and second wireless channels into packets, and keeping packets with the least errors.
 11. The method of claim 8, further comprising determining the wireless channel with the least assessed link quality, and avoiding use of the wireless channel determined to have the least assessed link quality.
 12. The method of claim 8, wherein adjusting includes: adjusting power to transmit or receive a communication signal over the wireless communication link based on the assessed link quality; adjusting a symbol transmission rate based on the assessed link quality; adjusting a receive signal strength indicator (RSSI) threshold based on the assessed link quality; adjusting a packet length based on the assessed link quality; adjusting a selection of a diverse antenna based on the assessed link quality; or adjusting a transmission frequency by changing channels based on the assessed link quality.
 13. The method of claim 8, further comprising: assessing a link quality for each available communication channel not in use; summing the link qualities to provide a sum; comparing the sum to a threshold; and reducing a receiver gain when the sum exceeds the threshold.
 14. The method of claim 8, wherein adjusting includes first adjusting wireless communication by adjusting at least one of power, symbol transmission rate, receive signal strength indicator (RSSI) threshold, packet length, polarization or spacial location for a diverse antenna or transmission frequency to switch channels, and the method further includes: assessing link quality for the wireless communication link after first adjusting wireless communication; and if the assessed link quality is undesirable after first adjusting wireless communication, adjusting at least one other of power, symbol transmission rate, RSSI threshold, packet length, polarization or special location for a diverse antenna or transmission frequency by changing channels.
 15. The method of claim 8, wherein adjusting includes adjusting a receive signal strength indicator (RSSI) threshold based on the assessed link quality, and the method further includes: assessing link quality for the wireless communication link after adjusting the RSSI threshold; if the assessed link quality is undesirable after adjusting the RSSI threshold, adjusting a selection of a diverse antenna based on the assessed link quality; assessing link quality for the wireless communication link after adjusting the selection of the diverse antenna; if the assessed link quality is undesirable after adjusting the selection of the diverse antenna, adjusting a transmission frequency by changing channels based on the assessed link quality.
 16. A system, comprising: a plurality of devices configured to wirelessly communicate with each other, wherein the plurality of devices includes a battery-operated hearing assistance device configured to be worn by a person, the hearing assistance device including a signal processing circuitry connected to a microphone and a receiver; at least one of the plurality of devices including a link quality management device configured to: assess a link quality for a first wireless communication channel, wherein the link quality management device is configured to assess a signal-to-noise ratio for the first wireless channel for use in assessing the link quality; provide channel metrics indicative of the assessed quality for the first wireless communication channel, wherein the channel metrics includes channel metrics indicative of the assessed signal-to-noise ratio; and adjust wireless communication over the first wireless communication channel using the channel metrics for the first wireless communication channel, wherein the link quality management device is configured to dynamically adjust a receive signal strength indicator (RSSI) threshold over the first wireless communication channel using at least the assessed signal-to-noise ratio for the first wireless communication channel.
 17. The system of claim 16, wherein: the link quality management device includes a peak detector configured to detect a peak value for a received signal and an average detector configured to detect an average value for the signal; and the link quality management device is configured to use the peak detector and the average detector to determine if an available channel has a desirably low peak value and a desirably low average value, and to provide wireless communication over the available channel that has the desirably low peak value and the desirably low average value.
 18. The system of claim 17, wherein the link quality management device is configured to weight the average value for the received signal higher than a peak value for the received signal.
 19. The system of claim 17, wherein: the battery-operated hearing assistance device is configured to transmit wireless signals near a noise floor; and the link quality management device is configured to measure RSSI on a per packet basis, and set an adaptive RSSI threshold using RSSI values attained during and between packet reception to increase link margin in receiving a packet form the battery-operated device.
 20. A method, comprising: assessing link quality for a wireless communication channel between a battery-operated hearing assistance device and at least one other device; providing channel metrics indicative of the assessed quality for the first wireless communication channel, wherein the channel metrics includes channel metrics indicative of the assessed signal-to-noise ratio; and adjusting wireless communication based on the assessed link quality using the channel metrics, including dynamically adjusting a receive signal strength indicator (RSSI) threshold over the first wireless communication channel using at least the assessed signal-to-noise ratio for the first wireless communication channel.
 21. The method of claim 20, wherein: the battery-operated hearing assistance device is configured to transmit wireless signals near a noise floor; and the method further comprising measuring RSSI on a per packet basis, and setting an adaptive RSSI threshold using RSSI values attained during and between packet reception. 